RBL 12 pounder 8 cwt Armstrong gun
| RBL 12 pounder 8 cwt gun | |
|---|---|
At the Australian War Memorial, Canberra
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| Type | Field gun |
| Place of origin |
 United Kingdom
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| Service history | |
| In service | 1859 - 19?? |
| Used by | British Empire |
| Wars |
New Zealand Land Wars Second Opium War |
| Production history | |
| Designer | W.G. Armstrong Co. |
| Manufacturer | Royal Gun Factory |
| Unit cost | £79 - £170 |
| Specifications | |
| Barrel length | First model: total 84 inch, bore 73.375 inch New model: total 72 inch, bore 61.375 inch (20.46 calibres) |
| Crew | 9 |
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|
|
| Shell | 10 lb 11 oz Shrapnel 11 lb 4 oz common shell 10 lb 8 oz Segment 10 lb 9 oz case |
| Calibre | 3-inch (76.2 mm) |
| Breech | Armstrong screw with vertical sliding vent-piece (block) |
| Muzzle velocity | 1,239 feet per second (378 m/s) |
| Effective firing range | 3,400 yards (3,100 m) |
The Armstrong Breech Loading 12 pounder 8 cwt, later known as RBL 12 pounder 8 , was an early modern 3-inch rifled breech-loading field gun of 1859.
The gun incorporated some advanced features for its day. It was one of the first breech-loaders: shell and gunpowder propellant were loaded through the gunner's end of the barrel, rather than through the muzzle as in previous guns, allowing a higher rate of fire. The shells were coated with lead, which engaged spiral grooves cut inside the barrel ("rifling") and caused the shell to spin rapidly in flight and hence imparted far greater accuracy and range than previous guns. The lead coating effectively sealed the gap between shell and barrel and eliminated the wastage of propellant gases, previously known as "windage", and hence only half the amount of gunpowder propellant as previous was required.
The barrel was of wrought iron, "built up" of a tube with additional layers heated and then shrunk over it as they cooled. The result was a "pre-stressed" barrel: the interior of the barrel was under compression from the layers shrunk over it, so that the heat and pressure of firing did not stretch it. Hence the barrel was smaller and lighter than previous guns.
The gun was the British army's first rifled breechloading field gun, superseding the SBML 9 pounder 13 cwt in 1859. The gun as originally adopted had a barrel 84 inches long, with a bore of 73.375 inches. The Royal Navy adopted a version with a 72-inch barrel, with a bore of 61.375 inches, by simply cutting 12 inches off the end, and from 1863 the shorter length was incorporated into a common version for both land and sea use.
Unfortunately, the new technology involved required higher standards of gun maintenance and gunner training than the British army was prepared to provide, with the result that in service the gun had a reputation for unreliability. In 1871 Britain reverted to muzzle-loading guns, which were cheaper and fired much cheaper ammunition, with the RML 9 pounder 8 cwt.
The Colony of Victoria (today the State of Victoria, in Australia), sold 6 Armstrong 12-pounders to New Zealand for use in the Māori wars, for a sum of 3,592 pounds 1s 8d with equipment and ammunition. They travelled from Melbourne on 7 November 1863 on the troopship Himalaya, and arrived in Auckland on 11 November 1863.
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Wikipedia